I am new to the NAS world, so I think, naively, about the NAS operating system as I do about any Linux system: If the boot sector is where the boot code expects it, any size drive that is big enough will work.

I bought a chassis on ebay, and I'm trying to resurrect it. I looked for information on drive selection, and did not find anything. I looked for generic advice on which drives are best for NAS use, and did not find much.
One article suggested that green drives don't actually save much power if they are only spinning 3 hours a day. I, however, am more concerned about the power usage when the drive is in use: almost all drives are designed to meet their life expectancy spec if the drive housing temperature is limited to 60 degC or below. I think that it is safe to infer that operating at a lower temperature is better. I worked in the HDD industry for years, 60 degC is the temperature at which "you can hold the drive in your hand, but not for long."
Just for fun, look at this chart http://www.antiscald.com/prevention/gen ... /table.php, even though it is for immersion in water, it demonstrates that the "pain curve" gets very sharp at 60 degC. Experienced engineers could estimate 60 +/- 3 C if they could get a hand on it.

The OLD drive "Non-recoverable read errors per bits read" is an order of magnitude BETTER than the new drive.

Newer drive have 6GB/Sec transfer, vs 3GB/Sec for older units - even in a system with Giga Bit Ethernet, does it matter?

Please let us know what your research turns up!

Final Disclaimer: I am discussing Western Digital here only because I just bought one. I (and most other HDD engineers that have shared an opinion with me) think that all the big players make good drives - if a company is shipping units to the big computer integrators they simply can not stay in business shipping junk.
Really Final Word: Beware drives that have been shipped with inadequate packaging, or handled by careless/untrained individuals. Bulk drives are packed for shipping to OEMs, manufacturers often refuse to honor the warranty for units that are designated OEM and then are sold retail.